In a medium mixing bowl stir together bread crumbs, milk, onion, parsley, Parmesan cheese, garlic powder, and pepper.
Add meat; mix well.
Shape into four 3/4 inch thick patties.
Place meat patties on the unheated rack of a broiler pan.
Broil 3 inches from the heat for 6 minutes.
Turn and broil 6 to 8 minutes more or till meat is no longer pink.
Top each burger with 1 slice of tomato.
Sprinkle with oregano, then mozzarella cheese.
Broil 1 to 2 minutes more or till cheese is melted.